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The present invention relates generally to dispersing actives into the air. It appears especially well suited to disperse insect control actives such as insect repellants and insecticides to control flying insects that may be present in indoor rooms.
It is beneficial to control flying insects within buildings. Insect control is also useful in other areas, including screened areas such as tents, that are subject to invasion by flying insects.
Devices that dispense insecticide vapors to control insects in such settings traditionally require heating or burning a liquid or solid to disperse the active ingredients. Products that use a heat source may require a safe burning site, e.g. in the case of insect coils, or may require a source of electrical current for typical heated evaporation products.
Thus, techniques have been designed to dispense such insect control actives (and other actives such as fragrances and deodorizers) by employing passive evaporation, i.e. evaporation without the application of heat. For example, WO96/32843 describes an insect strip to control flying insects, the strip having a substrate that is impregnated with an active ingredient available for passive evaporation. The active ingredient is selected from transfluthrin, prallethrin, vapothrin, tefluthrin, esbiothrin, dichlovos (DDVP), and combinations thereof.
Co-pending U.S. patent application Ser. No. 09/326,446, filed Jun. 4, 1999, assigned to the assignee of the present invention, discloses insect control ingredients that can passively evaporate from non-absorbing substrate strips (such as those made of Barex(copyright) polymeric film) to control flying insects. The disclosures of this patent application and all other patent applications, patents, and publications referred to herein are incorporated by reference as if fully set forth herein.
The vaporizable active ingredients of the aforementioned insect control devices are typically stored for shipment, sale, and home storage in some type of separate, tear open, vapor impermeable pouch or other container. The pouch or other container prevents the active ingredient from prematurely evaporating before insect control is required and also provides a way of avoiding having those handling the device accidentally contact the active during such non-use situations. Thus, in the past, both a substrate from which the active could passively vaporize and a sealed barrier pouch or container were needed. See also U.S. Pat. No. 5,487,932.
However, this added material and assembly cost money. This is a significant problem, because these devices are often intended for use in areas of the world where the average income is exceedingly low while, at the same time, the rate of malaria and other flying insect borne disease is high. Thus, a need exists for developing ways to reduce the cost of such passive evaporation strips while still providing the functions of both a dispensing substrate and a sealed pouch or container for that substrate prior to its being needed for use.
In one embodiment, the invention provides an article to dispense a vaporizable active selected from the group consisting of insect control ingredients and fragrances, deodorizers, and other air modification volatile ingredients. The article has a pouch with opposed and, preferably, single layer walls that are releasably sealed together to define an interior cavity therebetween. An inside surface of at least one of the walls is coated with a vaporizable active. The term xe2x80x9ccoatedxe2x80x9d is herein defined to include all means of surface treating such that a surface carries the material with which it is coated. The pouch is impermeable to the active contained therein and has an outside, exposed surface. Preferably, no separable, active-bearing article is contained within the pouch with, instead, the inside surfaces of the pouch being the only structure of the article coated with the vaporizable active.
In preferred embodiments, the pouch is formed by folding a strip of polymeric film upon itself, with the fold constituting a first side of the pouch. The remaining sides are releasably sealed. Preferably the pouch is generally rectangular, having the folded side and three remaining, sealed sides. Alternatively, two sheets of the film could be placed on each other and then sealed on all sides, again preferably in rectangular shape with four, sealed sides. For ease of description, and unless a contrary meaning is clearly intended in the context, pouches or sheets of material will be referred to has having four xe2x80x9csidesxe2x80x9d even if their shape is actually rounded, irregular, or has in literal fact more than four sides, the reference to a shape having four sides simply intended to describe a closed figure. Thus, a circle, oblong, square, triangle, pentagon, or other closed figure will be equally referred to as figures having xe2x80x9cfour sides.xe2x80x9d
The sealing is preferably heat sealing, such as hot wire sealing or sealing using a heat sealing bar, preferably the sealing bar being 0.5 mm-2.5 mm wide. A narrow, hot seal is desirable for creating a vapor-tight seal. If only a liquid-tight seat is desired, as will be discussed below, a broader seal width created with a cooler sealing device is preferable.
The pouch can have, extending from its end, a portion that is free of the active, which portion has a through hole or is in the form of a hanger. Alternatively or additionally, the extending portion can be in the form of a pair of unsealed flaps extending from the opposed walls at a sealed side of the pouch to form tabs extending beyond the point of sealing to facilitate the opening of the pouch. If desired, the flaps can be of different sizes, and one of the flaps can include a through hole.
The interior surface of the pouch can be textured, corrugated, or otherwise modified to increase its surface area, thus providing the ability to hold a greater amount of volatile active than would otherwise be the case, extending the time over which volatile remains to be released from an opened pouch.
In a preferred embodiment, the pouch is subdivided by an intermediate seal into two chambers, the remaining margins of both chambers being sufficiently sealed as to prevent passage of the volatile active even when in vapor form. At least one interior surface of a first of the two chambers is coated with the volatile active to be dispensed. In contrast, the interior surfaces of the second, remaining chamber are free of any such coating of volatile active. The end of the second chamber remote from the intermediate seal is tearable to allow a user to open the second chamber to grasp the opposed walls thereof to then part the intermediate seal and expose the interior surfaces of the first chamber. It will be apparent that this arrangement allows a user to tear open the first chamber while avoiding having to touch any volatile active-coated surface.
Sometimes an intermediate seal made sufficiently complete to contain volatile active even in vapor form also is mechanically strong enough that a user can tear the pouch walls before the intermediate seal opens, resulting in an unreliably openable product. To avoid this, in the most preferred embodiment, the intermediate seal is made adequate to prevent the passage therethrough of the volatile active when it is in liquid or solid form, even though it may not be adequate to prevent the passage of active in vapor form. This lesser sealing requirement allows the intermediate seal to also be sufficiently releasable that the intermediate seal opens without any tearing of the opposed walls. Vapor is contained within the second chamber by the vapor-tight seal around its remaining margins. This arrangement provides a reliably openable article that remains vapor tight.
Preferably the opposed walls at a sealed margin of the second chamber at a location remote from the intermediate seal include a notch that provides a point of mechanical weakness to make easier a user""s tearing open the end of the second chamber. While a wide variety of vaporizable insecticides, repellants, and insect growth regulators may be suitable insect control ingredients, it is highly desirable for insect control purposes that the control agent be selected from the group consisting of transfluthrin, tefluthrin, prallethrin, vapothrin, esbiothrin, dichlovos, and combinations thereof.
Preferred materials for forming the pouch are 1.0 mm to 3.0 mm thick films of acrylonitrile methacrylate copolymer, polyester, polyvinyidene chloride, orientated polyethylene, nylon, polyvinyl alcohol, orientated polypropylene, and ethylene vinyl alcohol. They are all vapor impermeable, heat sealable, and provide suitable relatively non-absorbent surfaces that can be coated with the active. Alternatively, laminated or otherwise layered films can be used, including multi-layered films in which individual layers provide only some but not all such features as barrier strength, sealability, an active release surface that can be coated with an active without absorbing or chemically reacting with it. For example, strong films that would not be good active release surfaces can be metallized or combined with a metal foil layer that can thus provide a release surface. Sealant layers can include such materials as, for example, polypropylene, polyethylene, polyethylene tetephthalate-based films, and ethyl vinyl alcohol.
Most preferably, the insect control ingredient is transfluthrin, and the walls are formed of a modified acrylonitrile methacrylate copolymer such as the material sold as Barex(copyright) 210 or Barex(copyright) 218 (both available from BP Chemicals/Amoco).
A further form of the invention is a method of forming such a pouch where one obtains a pocket formed of polymeric film, injects a selected active in the pocket, and so heat seals the pocket as to form an enclosed pouch with the active releasably trapped therein.
In another form, the invention provides a method of controlling flying insects. One obtains one of the above articles, opens the pouch to form a strip, and then hangs the strip in a selected environment such that an insect control ingredient can vaporize into the environment.
In yet another form, the invention provides an alternative embodiment of the method of forming such a pouch. One obtains a polymeric film, coats a surface of the film with the active, folds the film upon itself so that the coated surface is an inward surface, and heat seals at least three peripheral sides of the resulting structure to form an enclosed pouch with active releasably trapped therein.
In still another form, the invention provides a further alternative embodiment of the method of forming such a pouch. One obtains two sheets of polymeric film, coats a surface of at least one of the sheets with the active, places the sheets upon each other so that said surface faces the other sheet, and heat seals peripheral sides of the resulting structure to form an enclosed pouch with the active releasably trapped therein.
It will be appreciated from the discussion herein that the inventors of the present invention have identified vapor impermeable, releasably sealable materials that are also suitable to be a substrate for an active insect control ingredient. The present invention thus avoids the need for a separate pouch to house the coated substrate.
Preferably, hot knife and bar heat sealing processes are used to releasably seal the pouch. In this way, the pouch can be hermetically sealed to prevent the insect control ingredient from escaping during storage, but can be easily peeled apart for use.
Another advantage is that the strip substrate can be formed to have a free end extending from one end of the pouch, that free end being kept free of the insect control ingredient and thus being available to be handled by a user to open the pouch or hang the strip substrate without having to contact the insect control ingredient.
The present invention thus provides a very low-cost vapor dispersing article wherein the strip substrate acts as a base for the vaporizable active and also forms the sides of a vapor impermeable pouch.
These and still other advantages of the invention will appear from the following description. In the description reference is made to the accompanying drawings which from a part hereof and in which there is shown by way of illustration preferred embodiments of the invention. However, the claims should be looked to in order to judge the full scope of the invention.